The invention relates to a spring shaft for cleaning pipelines.
Such spring shafts, which are also called cleaning coils, consist usually of a coiled drawn steel wire of round cross section with a smooth surface. They are provided at their ends with couplings for connecting to a great variety of tools, such as drills, cutterheads, thrashing chain heads, pipe brushes, root cutters, mud drills, etc. The machines that drive them and their manner of operation are explained in the detailed description.
Such spring shafts, which are also called cleaning coils, consist usually of a coiled drawn steel wire of round cross section with a smooth surface. They are provided at their ends with couplings for connecting to a great variety of tools, such as drills, cutterheads, thrashing chain heads, pipe brushes, root cutters, mud drills, etc. The machines that drive them and their manner of operation are explained in the detailed description.
The known spring shafts are substantially of only a drive character. The mounted tools are inserted into clogged pipelines by the spring shaft, which can also be composed of several spring shafts, and “work their way” through elbows, branch lines etc. They are withdrawn by reversing their sense of rotation, and in the case of stubborn blockage they can also perform periodical forward and reverse movements.
DE 38 32 716 C2 discloses a spring shaft with a cross section in the shape of a rectangle or trapezoid, from which two opposite edges run parallel to the axis of the spring shaft. The outer edge of these helically running edges lies in an imaginary cylindrical surface if one considers the outstretched position of the spring shaft. Thus the corners of this cross section which also ran helically can exercise no cleaning action on the inner walls of pipes, even when the spring shaft is passed through bends or elbows because in these cases the outer edge of the cross section contacts the bend only tangentially on its smallest radius of curvature; in other words the cross sectional edges in the pipe bend cannot come in contact with the inside surface of the pipe.
The known apparatus serves for lining the inner walls of pipes, and at the end of the spring shaft a plurality of successive rotationally symmetrical spreader bodies are arranged for a fluid coating material which is fed through a hose running inside of the spring shaft, and is distributed on the pipe wall by the spreader bodies when the spring shaft is withdrawn. The spring shaft has only a driving function. For the sake of limiting changes in diameter when the spring shaft is rotated forward and backward, the latter has a rectangular or trapezoidal cross section defined by formulas. The use of the spring shaft itself as a cleaning device is neither disclosed nor suggested, since it is expressly stated that, for cleaning the pipe's inside wall, cleaning devices must be attached to the forward end of the spring shaft.
The invention is addressed to the problem of improving such spring shafts so that, while preserving their driving function itself, they can exercise a cleaning action.
The solution of the stated problem is accomplished according to the invention by the features in the specific part of claim 1.
The stated problem is solved to the full extent by this solution, i.e., while retaining their driving function itself, they exercise a cleaning action and scrape, so to speak, even stubborn incrustations from the pipe walls, which can consist of ceramics, cast iron or plastic.
It is especially advantageous, as a result of further embodiments of the invention, if, either individually or in combination:                the exterior is provided with at least one longitudinal groove following the coils,        the cross section of the coils is a square whose one surface diagonal run at least substantially radially to the axis of rotation,        the exterior is provided with a profile in which projections and grooves alternate,        the projections are sharp-edged at least in the circumferential direction of the coil axis,        the projections are surrounded by the grooves,        the grooves form two groups of which the grooves of the one group run substantially in the circumferential direction of the coil axis and the grooves of the other group run at an angle thereto,        the grooves of both groups intersect at an angle between 30 and 60 degrees,        the projections overlap in the circumferential direction of the coil axis such that drive jaws of a machine driving the spring shaft cannot drop into the grooves, and/or if        the projections are rhomboidal in plan.        
The shaping can be done by rolling, grinding or milling, also on the wire before winding, if desired. In this case heed must be paid only to precise guidance in the winding.